1. Field of the Invention
The present invention is generally related to oil which is used in machinery such as internal combustion engines and electrical transformers, and more particularly related to sensor and method for the on-line detection of the oil level, and the oil deterioration which occurs in the presence or absence of water.
2. Description of the Prior Art
Sensors and methods for detecting oil deterioration and oil level are well known. The following 21 patents and published patent applications are the closest prior art references which are related to the present invention.    1. U.S. Pat. No. 4,517,547 issued to Gary et al. on May 14, 1985 for “Water-In-Fuel Sensor Circuit And Method” (hereafter the “Gary Patent”);    2. U.S. Pat. No. 4,646,070 issued to Yasuhara et al. on Feb. 24, 1987 for “Oil Deterioration Detector Method And Apparatus” (hereafter the “Yasuhara Patent”);    3. U.S. Pat. No. 4,764,258 issued to Kauffman on Aug. 16, 1988 for “Method For Evaluating The Remaining Useful Life Of A Hydrocarbon Oil” (hereafter the “Kauffman Patent”);    4. U.S. Pat. No. 5,540,086 issued to Park et al. on Jul. 30, 1996 for “Oil Deterioration Sensor” (hereafter the “Park First Patent”);    5. U.S. Pat. No. 5,929,754 issued to Park, et al. on Jul. 27, 1999 for “High Sensitivity Capacitive Oil Deterioration and Level Sensor” (hereafter the “Park Second Patent”);    6. U.S. Pat. No. 6,297,733 issued to Park, et al. on Oct. 2, 2001 for “Stable, Reliable Capacitive Oil Deterioration And Level Sensor” (hereafter the “Park Third Patent”);    7. U.S. Pat. No. 5,377,531 issued to Gomn on Jan. 3, 1995 for “Portable Oil Change Analyzer” (hereafter the “Gomn Patent”);    8. U.S. Pat. No. 4,733,556 issued to Meitzler et al. on Mar. 29, 1988 for “Method And Apparatus For Sensing The Condition of Lubricating Oil In An Internal Combustion Engine” (hereafter the “Meitzler Patent”);    9. U.S. Pat. No. 6,278,282 issued to Marszalek on Aug. 21, 2001 for “Method And System For Determining Oil Quality” (hereafter the “Marszalek Patent”);    10. U.S. Pat. No. 6,590,402 issued to Wang et al. on Jul. 8, 2003 for “Engine Oil Condition Sensor” (hereafter the “Wang First Patent”);    11. U.S. Pat. No. 6,535,001 issued to Wang on Mar. 18, 2003 for “Method and device For Sensing Oil Condition” (hereafter the “Wang Second Patent”);    12. U.S. Pat. No. 6,577,112 issued to Lvovich et al. on Jun. 10, 2003 for “Method And Apparatus For On-Line Monitoring Of Quality And/Or Condition of High Resistive Fluids” (hereafter the “Lvovich Patent”);    13. U.S. Pat. No. 7,143,867 issued to Chopra on Dec. 5, 2006 for “Electronic Oil Level Detection And Replacement System” (hereafter the “Chopra Patent”);    14. United States Patent Application Publication No. 2006/0232267 issued to Halalay et al. on Oct. 19, 2006 for “Determining Quality Of Lubricating Oils In Use” (hereafter the “Halalay Publication”);    15. U.S. Pat. No. 6,718,819 issued to Schoess on Apr. 13, 2004 for “Oil Quality Sensor System, Method and Appatus” (hereafter the “Schoess Patent”);    16. U.S. Pat. No. 6,278,281 issued to Bauer et al. on Aug. 21, 2001 for “Fluid Condition Monitor” (hereafter the “Bauer Patent”);    17. U.S. Pat. No. 6,014,894 issued to Herron on Jan. 18, 2000 for “Motor Sensor System” (hereafter the “Herron Patent”);    18. U.S. Pat. No. 6,917,865 issued to Arai et al. on Jul. 12, 2005 for “Engine Oil, Degradation-Determining System And Method, And Engine Control Unit” (hereafter the “Arai Patent”);    19. United States Patent Application Publication No.: 2006/0114007 issued to Cho on Jun. 1, 2006 for “Apparatus, A method, And Measuring Sensors For Scanning States Of Engine Oil” (hereafter the “Cho Publication”);    20. China Patent No.: 03140986.5 issued to Sun on Dec. 3, 2003 for “Methods For Detecting Deterioration In Oil” (hereafter the “Sun Patent”); and    21. United States Patent Application Publication No.: 2009/0063060 issued to Sun on Mar. 5, 2009 for “Methods for Detecting Oil Deterioration and Oil Level” (hereafter the “Sun Publication”).
The Gary Patent discloses an invention of a water-in-fuel sensor circuit and method. The invention includes a reference capacitor coupled in parallel with a variable capacitor which is immersed in a fuel of a fuel tank, wherein two capacitors are alternately charged and discharged by an oscillator. Water in the fuel will cause increase of the effective capacitance value of the variable capacitor which reduces the absolute magnitude of the current that is detected. The absolute magnitude of the detected current can be utilized to indicate excessive water levels in the fuel.
The Yasuhara Patent illustrates an oil deterioration sensor and method. The oil deterioration sensor is comprised of a voltage divider which is constructed by a sensor capacitor and a fixed capacitor, wherein a constant frequency AC voltage source is applied to the voltage divider. Therefore a developed voltage across the sensor capacitor corresponds to the dielectric constant of the lubrication oil, from which the oil deterioration can be detected. The frequency of the AC voltage ranges from 50 KHz to 500 KHz.
The Kauffman Patent discloses a method for evaluating a remaining useful life of a hydrocarbon oil containing at least one additive species. A voltammetric analysis is applied to test a remaining amount of the additive, which results in an amount of the redox current corresponding to the remaining amount of the additive. Therefore, the remaining useful life can be concluded in accordance with the magnitude of the current.
The Park First Patent discloses an oil deterioration sensor. The sensor includes an oil deterioration sensor capacitor which is constructed with two metal plates, and a total reference capacitor which includes an external fixed reference capacitor. The capacitances of the respective oil deterioration capacitor and total reference capacitor provide an engine oil deterioration indication for the oil deposited within a gap of the metal plates. The oil deterioration sensor further includes a temperature sensitive resistor thermally connected to a substrate of the sensor for providing a temperature adjustment to the engine oil deterioration indication, and a circuitry utilizing the capacitances of the respective oil deterioration sensor capacitor and total reference capacitor to generate the engine oil deterioration indication.
The Park Second Patent discloses a combination of a capacitive oil deterioration and oil level sensor. The sensor comprises a conductive cylindrical housing member that includes a conductive shielding member defining a ground electrode, and a conductive inner member defining a measuring electrode. The sensor also includes electronics adapted to generate signals indicative to the deterioration of the oil deposited within a gap of two electrodes and a level of the oil along the length of the cylindrically shaped sensor. The oil level is monitored from detecting a ratio of the capacitance of oil dielectric constant over the capacitance of the oil level as C∈/CL.
The Park third Patent discloses a sensor which has a similar main structure as the sensor of the Park Second Patent. In addition, the patented sensor applies electronics including at least one isolating capacitor to eliminate a flow of current between two electrodes that may cause a build up of an unwanted material on the two electrodes that define the capacitor. This build up of the unwanted material may cause an undesirable effect in the sensor output signal. The Park Third Patent further discloses the capacitance C∈ of the oil deterioration and level sensor capacitor is proportional to ∈ times L, where ∈ is the dielectric constant of the oil and L is the length of the inner electrode. Therefor, the oil level affects the length of the inner electrode, which also affects the capacitance of the sensor.
The Gomm Patent discloses a portable oil change analyzer for a laboratory oil test, which is comprised of a viscosity analyzer and a contamination analyzer. The contamination analyzer is based on an optical mechanism, where increase of contaminates in oil results in decrease of a light intensity for an incident light after passing through the oil sample. The oil quality is determined by results from both viscosity and contamination tests.
The Meitzler Patent discloses an oil deterioration sensing system comprising an identical reference capacitor and sampling capacitor immersed in the respective fresh oil and sample oil under test. The system tests change of responded frequencies of the tested oil when both capacitors are under excitation of applied frequencies. Results of the test indicates change of the responded frequencies is consistent with change of the viscosity of the oil which is related to the aging of the oil.
The Marszalek Patent discloses a method for detecting quality of lubricating oil, which includes a sensor having two electrodes. The method includes applying a potential of a first amplitude to the electrodes immersed in an oil in use, testing a first voltage phase lag, increasing amplitude of the potential to a second amplitude, testing a second voltage phase lag. Therefor, the patented invention can determine the quality of the oil based on the voltage phase lags.
The Wang First Patent discloses a method of detecting engine oil if it is contaminated by presence of antifreeze. The method includes applying a series of different voltages to a sensor immersed in an oil in use, testing a corresponding series of the current sensor output voltages, determining a voltage difference between each of the current sensor output voltage relative to a reference voltage, thereby determining if presenting the antifreeze in the oil after comparing the voltage differences.
The Wang Second Patent discloses a device for testing oil condition including an oil condition sensor having electrodes. The electrodes are separated by a gap that is filled with an engine oil. A processor connected to the sensor can be used to determine if the oil is at a first, second and third stage of oil degradation, which is corresponding to a first, second and third sensor output signal trend.
The Lvovich Patent discloses an apparatus and a method for monitoring a highly electrically resistive fluid. The method includes applying an AC signal that comprises at least two different AC electrical potentials, with at least one AC potential having a none-zero DC offset, measuring the fluid's electrical response including impedance and its real and imaginary components, thereby determining the fluid quality.
The Chopra Patent discloses an invention of electronic oil level and replacement system. The invention is based on the physical phenomenon that a position of a float member is dependent upon a level of the oil. Therefore, a change of the vertical position of the float member will cause a motion of a piston which opens or stops a passage to an oil reservoir. Therefore, the replacement system can work. Following the same mechanism, another float member can activate a lower oil level electric switch or an upper oil level electric switch according to the respective oil level, so that the oil level can be electrically detected.
The Halalay Patent illustrates a method to detect a change of oil resistivity over a period of elapsed times for an oil in use, which is consistent with to a change of the oil viscosity over the time. Therefore, the method can be applied to monitor oil deterioration including a remaining useful life of the oil.
The Schoess Patent discloses an apparatus for determining condition of the engine lubricating oil. The apparatus includes a sensor have a plurality of spaced apart electrode pairs on a nonconductive polymer film. A forcing-function waveform reactive circuit is applied to the sensor input electrode as a common voltage potential. The output current of the sensor output electrode is converted to an equivalent voltage. Based on the voltage values, the sensing apparatus will determine the oil's condition, and will therefore trigger a trouble code if the equivalent voltage falls within a predetermined range.
The Bauer Patent discloses a fluid condition monitor, comprising a capacitive spaced array electrode probe which is immersed in the fluid and is applied by an oscillating voltage. A first frequency of at least one hertz is applied and a corresponding first current of the electrode probe is measured. A second frequency is then applied and a corresponding second current is measured. Therefore a difference between the first and second current can be obtained, which can be used to predicate the fluid condition, as compared with a predetermined threshold value.
The Herron Patent discloses a motor sensor system for detecting the presence of water in a sealed oil chamber of an engine. The sensor system includes a plurality of flat conductive and insulative annular rings which are alternatively sandwiched together to be an assembly. The assembly is mounted on the propeller shaft in the sealed oil chamber of an engine. Each conductive ring is connected to a remote alarm circuit. In addition, the ring includes a plurality of radially inwardly extending probe sections which are circumferentially spaced around the propeller shift. Thus, if water enters the engine in running, a mixture of the oil and water spans one or more of the gaps formed between the complementary probe sections of the conductive element. Therefore, it completes the alarm circuit and provides an operator of the engine a warning of the water in the oil of the engine.
The Arai Patent discloses an engine oil degradation-determining system. The system applies a crankshaft angle sensor which detects the engine rotation speed of an internal combustion engine. Therefore, an electronic device calculates a cumulative revolution number indicative of a degradation degree of the engine oil. An oil level sensor detects an oil level of the engine oil, which is comprised of an upper limit switch and a lower limit switch. Basically, the upper switch monitors the oil level when it reaches a predetermined upper limit, and the lower limit switch monitors the oil level when it reaches a predetermined lower limit. Following this detection mechanism, the invention of the oil level sensor enables to monitor the oil level.
The Cho Patent Application Publication relates to an apparatus, a method, and measuring sensors for scanning engine oil of a vehicle. The invention includes a viscosity sensor which predominantly monitors the oil deterioration, and an oil level sensor which monitors the oil level. The oil level sensor in FIG. 8 has an input electrode 106 having a shape of a pipe and is installed to have an electric current applied thereto, and an oil level electrode 105 having a shape of a pipe installed apart from an inner surface of the input electrode 106 so as to receive the electric current from the input electrode 106. Therefore, the oil level is calculated on the basis of the capacitance and dielectric constant measured between the oil level electrode 105 and input electrode 106.
The Sun Patent discloses methods for detecting deterioration in oil, comprising a preferred dual sensor having reference and sensing capacitors. Therefore, variations of electrical properties of the sensing capacitor disposed in the oil, which are caused by the temperature variations of the oil, can be compensated by the same variations of electrical properties of the reference capacitor. This results in a temperature compensated electrical property of the sensing capacitor, which represents the oil deterioration. Following this concept, it can establish a profile of predicted temperature compensated electrical properties for the oil, which includes the properties of the respective new oil and spent oil. The profile corresponds to a range of usages from the respective new and spent oil. Therefore, a remaining usage ratio R of the oil can be calculated according to the obtained temperature compensated electrical property, which further determines a remaining usage of the oil as the remaining usage ratio times the range of usages. In addition, various methods are disclosed to detect presence of water in oil.
The Sun Publication discloses methods for detecting oil conditions including a top level of an oil in an oil system which is reduced to a top level of a threshold amount of the oil, a normal oil deterioration which occurs in the absence of water and has a confirmed remaining usage of the oil, and an abnormal oil deterioration which occurs in the presence of water. The methods include a first preferred embodiment which applies reference and sensing capacitors to obtain a measured temperature compensated electrical property of the oil. From which a quantitatively measured remaining usage is obtained so as to a predicted one for the oil. Therefore, the top oil level, or the normal or the abnormal oil deterioration can be concluded according to the measured remaining usage which is respectively larger than, or similar to, or less than the predicted one for the oil. A second preferred embodiment only includes the sensing capacitor for obtaining the measured temperature compensated electrical property of the oil. Variations to the embodiments lead to application of at least two sensing capacitors to monitor an uneven distribution of the oil deterioration or a full range of the level of the oil in the entire oil system.
It will be appreciated that the Sun Patent and Publication disclose unique methods, which apply a measurement sensor including a capacitor operated by an AC voltage for monitoring oil condition including deterioration and level of an oil in use. However, there is still a room for improving the conventional capacitor having two plates regarding its electrical characteristics, and output that is fundamental of the detection technology. This is because the output of the capacitor is limited by the gap between the two plates, which are electrically polarized according to the alternative polarities of the applied AC excitation. Therefore, the two plates alternatively having different electrical polarities are exposed to an electrical environment that surrounds the capacitor, so that there is a great chance for a cross talk between the capacitor and surrounding electrical environment if the capacitor is not electrically shielded.
There is a significant need to have a method and a sensor having improved output and electrical characteristics for detecting oil conditions including a top level of an oil system which is reduced to a top level of a threshold amount of the oil, and oil deterioration which occurs in the absence or presence of water, to significantly improve usage of the oil and protect machines which are lubricated by the oil.